On Thu, 16 Aug 2018 10:38:02 -0400
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> On Thu, 16 Aug 2018 18:51:15 +0900
> Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
>
> > Current trace-enable attribute in sysfs returns an error
> > if user writes the same setting value as current one,
> > e.g.
> >
> > # cat /sys/block/sda/trace/enable
> > 0
> > # echo 0 > /sys/block/sda/trace/enable
> > bash: echo: write error: Invalid argument
> > # echo 1 > /sys/block/sda/trace/enable
> > # echo 1 > /sys/block/sda/trace/enable
> > bash: echo: write error: Device or resource busy
> >
> > But this is not a preferred behavior, it should ignore
> > if new setting is same as current one. This fixes the
> > problem as below.
> >
> > # cat /sys/block/sda/trace/enable
> > 0
> > # echo 0 > /sys/block/sda/trace/enable
> > # echo 1 > /sys/block/sda/trace/enable
> > # echo 1 > /sys/block/sda/trace/enable
> >
> > Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > Cc: Jens Axboe <axboe@xxxxxxxxx>
> > Cc: linux-block@xxxxxxxxxxxxxxx
> > ---
> > kernel/trace/blktrace.c | 11 +++++++----
> > 1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> > index 987d9a9ae283..e67db1e8a000 100644
> > --- a/kernel/trace/blktrace.c
> > +++ b/kernel/trace/blktrace.c
> > @@ -1602,11 +1602,11 @@ static int blk_trace_remove_queue(struct request_queue *q)
> > struct blk_trace *bt;
> >
> > bt = xchg(&q->blk_trace, NULL);
> > - if (bt == NULL)
> > - return -EINVAL;
> > + if (bt != NULL) {
> > + put_probe_ref();
> > + blk_trace_free(bt);
> > + }
> >
> > - put_probe_ref();
> > - blk_trace_free(bt);
> > return 0;
> > }
> >
> > @@ -1619,6 +1619,9 @@ static int blk_trace_setup_queue(struct request_queue *q,
> > struct blk_trace *bt = NULL;
> > int ret = -ENOMEM;
> >
> > + if (q->blk_trace)
> > + return 0;
> > +
> > bt = kzalloc(sizeof(*bt), GFP_KERNEL);
> > if (!bt)
> > return -ENOMEM;
>
> Hmm, why not just do this? Does this fix it too?
Ah, yes, but we need to clear "ret" in that case.
Thanks!
>
> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> index 987d9a9ae283..10b2b9c5fd25 100644
> --- a/kernel/trace/blktrace.c
> +++ b/kernel/trace/blktrace.c
> @@ -1841,6 +1841,8 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
> mutex_lock(&q->blk_trace_mutex);
>
> if (attr == &dev_attr_enable) {
> + if (!!value == !!q->blk_trace)
> + goto out_unlock_bdev;
> if (value)
> ret = blk_trace_setup_queue(q, bdev);
> else
>
> -- Steve
--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>
